High blood levels of PSA (prostate-specific antigen) can signal prostate cancer, although other benign conditions also raise PSA levels. Men with high and rising PSA levels are usually advised to undergo prostate biopsies.

"On average, PSA declined by 4.1% after starting a statin," study researcher Robert J. Hamilton, MD, MPH, tells WebMD. "But what was really interesting was that the decline in PSA was proportional to the decline in cholesterol associated with the statin."

While the average PSA decline linked to statins was tiny, a bigger decrease was seen in men who started out with the highest PSA levels (2.5 ng/mL or more) -- but only among those who had the greatest decrease in cholesterol. These men had a 17.4% drop in PSA.

That could mean two different things, Hamilton suggests:

Statins may affect prostate biology.

Men taking statins may lower their PSA scores without lowering their risk of prostate cancer, making their PSA tests more difficult to interpret.

"Maybe these findings explain the reductions in advanced prostate cancer linked to statins," Hamilton says. "Or maybe we should worry about this decline in PSA. Could statins confuse the interpretation of PSA tests?"

Probably not, says Ian M. Thompson, MD, professor and chairman of the department of urology at the University of Texas Health Science Center at San Antonio. He says it's not clear how much those higher-than-average PSA scores would have gone down all by themselves -- the "regression to the mean" phenomenon often seen with clinical tests.

So if a man on statins chooses to undergo PSA screening and has a PSA test with a borderline score, Thompson would recommend simply repeating the test.

Continued

"People tend to act on a single PSA test. But a lot of data says wait three to six months and just repeat it -- often it comes back down," he says. "We don't really know if PSA screening reduces deaths from prostate cancer. Two ongoing studies, one in the U.S. and one in Europe, will answer that question."

Even if statins do lower a man's risk of prostate cancer -- something far from proven -- Thompson says the Hamilton study points only to a small drop in risk.

"There is abundant and very, very interesting basic science that suggests there might be an effect of statins on prostate cancer risk, but unfortunately the magnitude of the effect seen in this study wasn't much," Thompson says. "People should not go to their doctors and say, 'Start me on statins to reduce my risk of prostate cancer.'"

The Hamilton study, and an editorial by Thompson, appear in the Nov. 5 issue of the Journal of the National Cancer Institute. Hamilton is now with the University of Toronto, Ontario, Canada.